Vertical retort furnace



June 13, 1933.

9 Sheets-Sheet l F A HANSEN VERTICAL RETORT FURNACE Filed Dec.

INVENTOR.

ATTORNEY,

June 13, 1933. F. A. HANSEN VERTICAL RETOHT FURNACE Filed Dec. 24, 1950 9 Sheets-Sheet 2 INVENTOR. 424) El 3mm,

A TTORN June 13, 1933.

EA. HANSEN VERTICAL RETORT FURNACE Filed Dec. 24, 1950 9 Sheets-Sheet 4 Arromv June 13, 1933. F, HANSEN 1,913,386

VERTICAL RETORT FURNACE Filed Dec.

INVENTOR.

BY ATTORNEY? IE-EEEI June 13,1933. F. A. HANSEN 1,913,336

VERTICAURETORT FURNACE Filed Dec. 24, 1930 9 Sheets-Sheet 6 INVENTOR.

June 13, 1933. F. A. HANSEN VERTICAL RETORT FURNACE Filed Dec. 24, 1930 9 Sheets-Sheet '7 INVENTOR. 9M 61 J'EaM/MA V,

ATTORNE 9 Sheets-sheaf. 8

F. A. HANSEN VERTICAL RETORT FURNACE Filed Dec. 24; 19:50

June 13, 1933.

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ATTORNEY I 1 II \\\\\\\\\\\ili\\\\\\\ Ira-+7 HEATING 1 z II/// 3 37/ ##7 o a June. 13, 1933.

F. A. HANSEN VERTICAL RETORT FURNACE Filed Dec. 24, 193.0 9 Sheets-Sheet 9 INVENTOR.

ATTORN Y Patented June 13, 1933 V UNITED STATES PATENT OFFICE FRED A..HANSEN, F MILWAUKEE, WISCONSIN, ABSIG-NOR TO HEVI DUTY ELECTRIC COMPANY,,OF MILWAUKEE, WISCONSIN, A CORPORATION 01 WISCONSIN VERTICAL RETOBT FURNACE Application filed December 24, 1980. Serial No. 504 ,2379.

My invention relates broadly to retort furnaces and is herein illustrated as embodied and gas treatment operations.

One of the objects of my invention is to provide a vertical retort furnace so designed that any gas at atmospheric pressure or pressures above atmosphere may be utilized during the heat treatment of metals.

Another object of my invention is to provide a retort furnace having an inlet for protective or processing fluids so located that it deliver the fluids under forced circulation in such a manner that the inflowing fluids may be directly pre-heated and given movement at a relatively high velocity "before coming in direct contact with the parts sub- 'ject to heat treatment.

Still another object of my invention is to provide a construction of retort furnace which may be utilized for such processes as drawing or tempering; nitriding, carburizing, annealing or normalizing steel, applying a non-oxidizing finish to steel, and for the annealing of non-ferrous alloys in a protective atmosphere.

The general lltllliiy of the furnace of my invention, with its numerous applications,

makes it especlally desirable from the standpoint of initial investment and because of its construction, completes many processes in a shorter length of time than any furnaces heretofore known.

Another object of my invention is to provide a construction of furnace which may be kept constantly in operation after the heat treatment of any one batch while a preceding batch or charge is under-goinga cooling outside of the furnace, but still 1n a treating or protecting gas and forced circulating atmosphere.

A further object of this invention is to provide a furnace adapted for use with a processing gas produced by cracking or dissociation within the retort and which is constructed to provide an im roved and more eflicient cracking action or the production of gases such as gases containing carbon or nitrogen for cai'burizing or nitriding, respectively. Carrying out the improved cracking operation, the apparatus of this invention is constructed to include a furnace and a retort, into the latter of which the articles to be treated are placed and the processing as to be cracked is introduced. The retort is disposed in heat transferring association in the furnace whereby the gas is heated from a source exteriorly of the retort'. The retort is provided with means therein for forcibly directing the gas through an unobstructed heating space with the result that the gas is heated to a point where only partial dissociation occurs and a relatively high velocity is attained. At this point the forcedgas is caused to suddenly reverse its movement and to immediately forcefully impinge upon the articles bein treated. The mechanical agitation of the lmpingement causes substantially complete dissociation or cracking to produce the ultimate gas desired. This apparatus therefore provides an improved cracking action by efiiciently cracking the gas employed and by confining the dissociation to the region occupied by the articles under treatment. By the action described, the cracking takes place directly in and by contact with the articles.

A still further object of my invention is to provide means for establishing a forced circulation of gases around a charge under heat treatment both within and removed from a retort furnace.

Other and further objects of my invention will be understood from the specification hereinafter following and by reference to the accompanying drawings in which:

Fig. 1 is a perspective view of one embodiment of the furnace of my invention; Figs. 2 and 2a respectively denote a side elevation partially in. central vertical 1011 itudinal section; Figs.'3 and 3a respective y show a side elevation partially in central vertical longitudinal section showing a modified form of the improved furnace; Figs. 4 and 4a respectively show a top lan view partially in horizontal section of the furnace shown in Figs. 3 and 3a; Fig. 5 is a cross-sectional view through the furnace proper; Fig. 6 is a central vertical longi' tudinal sectional view of the charge-container after being lifted out of the furnace proper for allowing the charge to cool and further subject the same simultaneously to a gas treatment; Fig. 7 shows a side elevation of the upper part of the furnace lifted out of the furnace proper and supported by means of three depending pipe sections; and Figs. 8, 9, 10, 11 and 12 show detail views of the furnace.

In general, the furnace embodying the invention includes a heat insulated enclosure having an opening, a cover for said opening, a retort associated with said cover, means for establishing a circulation of fluids within the retort, the work to be treated preferably being disposed in a container within the retort constructed and arranged to promote the circulation of the fluids into contact with the work.

In all the forms shown in the drawings, the heat insulated enclosure includes an outer shell 1 having a bottom casting 2 and a top plate 3, all enclosing heat insulation material 4, surrounding a furnace chamber 5. The furnace chamber 5 may be heated by any suitable 'means, but for purpose of illustration, I have shown in Fig. 4 the chamber electrically heated by means of electrical resistance, such as 5a, lodged in under-cut grooves of refractories 6, such electrical resistance being connected to a power circuit not shown.

Referring to Figs. 3 to 7 the cover for the opening of the heat insulated enclosure includes a special form or retort rim casting 7 having a depending flange 8 projecting into a circular trough 9, formed by upwardly extending spaced flanges 10 and 11 which on this form are integral with the top plate 3. The casting 7 has another depending flange 12, to which is welded the upper end of a retort 13 which is hermetically tight in the sides and bottom. In the casting 7, in this instance where the weight of the charge does not require the retort to be directly supported on the bottom, the retort may be of sheet metal. I provide an annular groove 14, in which is placed a compressible gasket 15 which may be compressed by means of bolts 16 passing through said rim and a heat insulated cover 17 and which also detachably secure these parts together. Thus while the rim 7 forms a part of the cover for the enclosure, it also permits the retort to be removed from the main portion 17 of the cover so that the retort may be charged.

ner but which preferably is driven by the motor 20. Shaft 19 is made gas tight with respect to retort 50 by means of stufling box 21, having a gland 22 co-operating with any suitable packing 23 with provision for oiling the same through a tapped hole 24a either sealed with a removable plug 24 or connected with any suitable grease cup or other lubricating device, though I find when carburizing, suitable packing does not require lubrication because when carburizing, a deposit of carbon is obtained in the packing and around the shaft 19 to such an extent that it lubricates said shaft and at the same time stops a leakage which might otherwise result. That is to say, the lubrication is derived directly from the carbon atmosphere formed in the cracking process. The stuffing box holding the packing is operated under contact with an air cooling system which will be hereinafter described. As shown in Figs. 2 and 6 the stufiing box member is preferably separate from and detachably secured to the cover 17 the point between the same being sealed by a compressible gasket 23a.

For ooling the shaft 19 and keeping the stuffin box cool, I provide, at any suitable location, on the fan shaft, as above the gland 22, a centrifugal fan 25 of suitable design. \Vith the motor 20, driving shaft 19 even at a comparatively slow speed, such as 900 R.P.M., fan 25 centrifugally dislodges sufficient air at right angles to the shaft as to cause a suction of air past the stufling box and gland 22 as to cool shaft 19 at a comparatively short distance above gland 22, thereby keeping the stufling box cool and also preventing the overheating of motor 20 which might otherwise result.

Referring to Figs. 3 and 6 at a suitable I position on that portion of the shaft 19 which projects below the cover 17, I mount a centrifugal fan 26 generally similar to the fan 25 and adapted on revolving, to discharge air or fluid horizontally or centrifugally toward the cylindrical walls of retort 13 and thereby cause circulation or movement of air downward as indicated by arrows 27. To further assist this movement of the air the cover 17 may be modified as shown in Fig. 11 wherein the cover 64 for the retort has a curved bottom face 65 that tends to better deflect the fluid from a horizontal'to a downward flow.

Inside of the retort 13 I provide a basket or work container 28 appropriately perforated on its sides and bottom shown as apertures 42 to permit of a circulation of the gas therethrough. The top of this container has an opening 29, through which articles of the charge may be placed before attaching cover 17 to the rim casting 7. An apert-ured top member 29a having an annular inclined Wallis removably mounted on the to assist in centering the container when introduced into the retort, I provide radially tamer.

disposed lugs 31 on the sidesof the eoned above the cover 17 as b, tripod channel shaped legs 43 shown in igs. 3, 6 and], suitably fastened to pads 430 shown in Fig. 8. Currentfo'r operatin the motor 20 and for supplying energ to tiieheating elements 5a may be supplie by suitable conductors associated with a suitable source of supply.

I proyide means for forcing any desired, gas as liquid into the retort by means of inlet pipe 47- to. which is. attached supply pipe line 48 whi ch may be p'rovidedwithacontrol valve 73, see Fig. 10. The location of the inlet ipe 47; is just outside the perimeter of t efanand in a position such as tocause, an outward and downward flow of gas,,indicated by the arrows 27 which aspreviously notedunay be further assisted by the curved wall of the cover as indicated in Fig. 11. The outlet for the gases is through a,pipe 81. The cover 17 .is provided with apertures. at 47a and 81a to receive thelpipes i'l and 81 respectively and Wltll an. ,openingTOa to receive a pipe y a ,means of'rsupporting the cover and pro-- tecting the ifan 2b, when removed from" the" retort and placed onQ-the flooras'shown inhaving its inner end closed, see Fig.8, said pipes extending through the cover to aposition at the top of the retort and in the case of the,.cove1f;l7,, forming legs to provide Figs. 7; and-i 10. The upper end of pipe 70 is fitted ywithlga removable cap 71, said cap being removablefor the reception of a test thermocouple notshown. The pipes/17, 70 and 81 have a suitable fluid tight connection with the cover -l'las by welding.

Any suitable means for supplying current to motor 20 and :the heating resistancemay be employed. In .F igs. -3g and 3a, at 32 and; 33 are indicated connecting studs for the at;-

tachment of the powercireuit. At 34 and 35 are indicated; similarly connected studs con nected .to the electrical circuits of 32 and 33 and to the socket,"36, whichreceives a, con nector plug 37with-flexiblecable 38 ,which may in turn be connected to the motor leads tin flexible metallic conduit 39. As atlsa fcty means I provide a perforated cover 33a, cover all exposedterminals including n ther-n,

mocouple'not shown in these views; 1

In the construction shown in Figs. 3a

3a, the sand 85 in-trough 9 serves to substan-s tially seal the depending flange 8 with respect tothe furnace chamber, Gaskct lfi serves to-hermetically sea-l the coverg' upon'" the retort and the depending portion 369i- .to

the cover enters the ,retort and serves heatvlesses; g a a y i t In the operation of the furnace above described, with the charge in the container 28 and; the container. placed in the retort 13,

and th'e cover17 with itsfan in its position in a v -as shown in Fig.3, a protective or processing The fan motor 20 may be suitably mountgas isallowedto fio w through the inlet pipe actuatedby suitable couples attached to couple h eads. {I l-1e heated chamber 5 imparts heat to the retort 13 and consequently to the i i gases in or the fluids introduced intoi said f retort as wellasthe ,work to be treated in said-retort, The heated gases in the retort arekeptin circulation to be, heated by the retort and to colne intocontact with work in container 28, by the operation of the fan 26,, The speedand sizeof fan 26 is so se lected thatvthe volume of gas discharged from the fan is in excess of the gas that 7 a may enter the container 28 through per-l,

jforations 42in thesidewalls ,of said con,-

tainer, The excess: is consequently directed.

,upwardthrough the. perforations inthe bot- Itom of .the container and thenceupward past the chargeor work in said container and out through the opening in the top thereof where the suctionv of the fan 26.

assists in the rapid and proper mising of the inflowing new gas with the old gas, some of. the spent gas being allowed to pass out essing or treating gas incontact with the *through the outlet pipe 81 in regulatedv amounts desired. Thus it willbe noted that work being treated and that it also assures by its centrifugal action, the bringing of new fluid into ,heating association with the heated. walls of the retort, In the operation'of the furnace, I may introduce by way i of pipe 47, a gas orliquid which may readily volatilize into a gasfunder'theaction of the [moving gas above described since it will beobserved that the forced circulation will causethe gas to become rapidly heated and subsequently ,cracked,,vaporized or gasified.

Figs l, ,2iand 2ashow certain modificaitions gover ,that previously described, though where the parts-are similar, similar referenfce eharacters have been used. The furnace enclosure is generally the same with the outer enclosing casing provided by-the parts 1, 2 and 3 lined with theheat insulating lining;4,;about the, sides of which are placed --the refractory corrugated-plates 6 inwhich the heating means consists of return bend gresistance, coils 5a ;mount-ed in corrugated platesfia as showndndetailin U. S. Patent No. 1,768,865 to Edwin L. Smalley dated July 1,1930.

In Figs. 2 and 2a where the weight of the charge is of such magnitude as to require its support at the bottom, I provide means for permitting the retort to rest directly on the bottom of the furnace chamber and to still have an effective seal at the top. For this purpose I provide on the top rim 51 of the retort 50 a depending flange 52 which is free to expand upward or contract downward in the sand seal 82 disposed in the trough 53 of a rim casting 54 whose perimeter has a downwardly curved rim resting on a compressible asket 55 heldbetween it and the upturned ange 3a on the top plate 3. Annular plate members 84 carried by the bottom of trough 53 serve as bafiles between the furnace chamber and the sides of the retort 50 and deflect the heat from the greater portion of the casting .54.

The insulated cover 57 corresponding to the cover 17, is connected to the rim 51 by bolts as before and a gasket 56 forms a gas tight seal between these parts. The shaft 19 is journalled in the top cover and associated with the fans 25 and 26 and a motor 20 as in the first described construction.

In Figs. 2 and 2a a special form of work container is shown consisting of nested boxes 59 which may also be tote boxes that are per? forated at their sides and bottoms as indi.

cated at 5911. In order to have these nested boxes suitable for handling in one piece as when loading or unloading the retort, I have shown one method of interlocking the nesting boxes, as for instance by pins 44 passing through aligned perforations 60 in the box and a igned with perforated lugs 45 and 46 depending from the bottom of the box next above, said pins preferably located on 120 centers.

In Fig. 12 I have shown another method of interlocking the sections of the container. A section of the side wall 49 of one of the containers 59 is shown provided with an undercut lug 62 projecting below its bottom edge and another section of the side wall 61 of an adjacent container is provided with an outwardly extending lug 58 on its top edge.

Thus by shiftin the lower tote box or container to the le t, as indicated by the arrow 63 the lug 58 engages in the groove of lug 62 and thus secures adjacent boxes together. By this type of fastening I gain space in the tote box that is occupied by the pin method of interlocking, and do away with the inconvenience of loose parts. v

As before, to assist the flow of gases through the container formed by the boxes 1 59 the uppermost box carries the member 29a.

In this modified construction, in order to facilitate replacement of heating elements, and in order to permit separate temperature control in the upper and lower zones of the furnace chamber, connecting leads 75 of both upper and lower zone elements are brought out in a manner similar to studs 32, 33, 34 and 35, and are housed in protective guards 76 extending around the furnace shell 1. Protective guards 77, 78, 79.

having a toggle switch 41 for shutting on and off the circuit to the fan motor.

The action of the modified form of furnace is the same as that first described, it being understood that the cover 57 has fluid inlet and outlet pipes associated therewith as in the first form.

Thus far the operation of the furnace has been considered while the retort and charge were disposed within the same but by reason ofthe construction which ermits the retort,

its charge and the means 0r circulating the gases through retort beingremovable from the furnace enclosure as a unit, other advantages are attained.

Thus, upon completion of the heating cycle required for the charge in one retort,

such retort with its charge may be removed from the furnace by any suitable lifting and transferring means to a position where the protecting or processing fluid may be kept flowing while such retort and charge are cooling, as shown in Fig. 6. It should of course be understood that the retort being heated and the retort being cooled have separate fluid connections with separate valve controls so that each retort as to its atmosphere may be independently controlled. On the cover I may supply hoist attachment means such as a plurality of hooklike members 52 located on 120 centers. As soon as the complete charge .and the retort are removed from the furnace chamber, a second retort with its container and charge together with another cover and its motor driven fans may be placed in the furnace chamber. The flow of fluid may be continued through the cooling chamber for any required time. i

To facilitate the electrical connections of the driving motors 20 of the unit within and that without the furnace, lug connections are arranged as shown in Fig. 4a where plug 37 for'the motor 20 of the retort within the furnace is inserted in socket 36 while anotherplug may be inserted in socket 87 furnishing current to the driving motor of a Otherwise that portion of the charge near-' 0 est the retort will naturally cool more rapid 1;; than that portion of the charge nearest t e center of the retort or container. It may v therefore be noted that by the centrifugally 5 generated circulation of fluids in the retort both in the heating up and in the cooling of the charge therein the charge throughout is subjected to more uniform temperature conditions than without the fan. Grain growth exists in prolonged or excessive time under temperature; therefore the work performed in the furnace of my invention gives more uniform quality of product.

This method of operation of the furnace of my invention results in great economyin many processes. For example, in furnaces of other design, and using such furnace for nitriding, it may take ten hours to cool a charge in the furnace, which is a distinct loss of ten hours, and because the furnace of such design requires cooling of thecharge in the furnace, the furnace again has to be brought up to temperature for a second 011- eration, resulting in the loss of still more time.

When this apparatus is used in conjunction with a processing gas to be cracked as when carburizing or nitriding, with hydrocarbon gases or ammonia, respectively, the construction is designed to produce an improved cracking action as well as to promote the taking up or absorption of the carbon or nitrogen from the ultimate as products. In operation this is accomp ished by giving the fluid introduced a rapid movement in the heating space provided between. the wall of the retort and the work container and during the travel of the gases throughout this space, heating them to a point where partial dissociation occurs. Thereafter, on account of the forced movement, the gases are caused to he suddenly reversed in movement and to forcefully impinge against the articles being treated whereby a substantially complete cracking is effected immediately on the articles. The action is thus confined to the region occupied by the articles which makes for efliciency by intimate contact between the gas products and the articles and further by avoidance of the formation of ultimate products throughout other locations in thGpI 'GliOIlS- While I have describedaperforated container, it is to be understood that I may in some instances use a suspended rack on which coiled material, such as coils of wire or strip metal, may be placed.

- It isto be observed that under different processesthe furnace may be operated with a partial vacuum in the retort, or a pressure above atmospheric ressure. Since the retort as described has 0th inlet and out let pipes, I may create -a partial vacuum in the retort by keeping the supply inlet closed by means of a valve while wlthdrawing air or atmosphere from the retort to create such partial vacuum.

In place of a valve in the inlet pipe being used, a container such as a drip cup may be utilized where the pressure above the liquid level in the drip cup is the same as the pressure in the retort thereby permitting the fiow ofliquid from the drip cup under all conditions of ressure in the retort.

While I have descrihedmy invention in certain preferred embodiments, I desire that it is understood that certain modifications may be made and that no limitations upon my invention are intended other than are imposed by thescope of the appended claims.

For example, I may arrange a common drive means for the centrifugal mechanism of all of the retorts which ma be subjected to treatment in one furnace ciamber. The drive motor may be mounted upon the top rim of the furnace and a flexible drive connection' established to the centrifugal mechanism in the retort. In the claims where I have referred to the mounting of the drive motor on a part of the furnace structure, I have intended to cover various modifications of my invention which may suggest themselves to those skilled in the art. I may in some instances use a propeller type fan in the retort instead of the centrifugal type fan, each of which gives mechanical agitation or forced circulation of gases. Furthermore, in some. cases where the character of the articles to be heat treated does not necessitate nor make preferable the use of a containeror rack for the charge I may not usea container. On the other hand, I may in somev instances, such as in the case of heat treating crank or cam shafts, sus' pend such or similar articles from the cover.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a furnace, the combination of ,a furnace chamber, a vertical retort adapted to be inserted into said furnace chamber, a con tainer adapted to be mounted within said retort, said container comprised of interlocked horizontally disposed sections and perforated for the circulation of gases therethrough, means detachably connected with said retort for establishing a forced circulation of gases therein and through the perforations in said container, and separate means for injecting fluids into said retort.

2. A retort furnace comprising a furnace chamber, means for heating said chamber, a retort insertable within or removable from said chamber, a charge receiving container disposed within said retort and comprised of interlocked horizontally disposed sections, a removable cover at one end of said retort, a drive motor supported withrespect to said removable cover, a stuffing box carried by said cover, a drive shaft connected with said drive motor and journalled in said stufling box, a fan connected with said drive shaft and operative within said retort for establishing a forced circulation of gases, and means for establishing low pressure within said stufiing box for effecting a deposit of material from said retort for maintaining said shaft in a condition of lubrication.

3. A retort furnace comprising in combination a furnace chamber, heating means within said chamber, a retort insertable into or removable from said furnace chamber, a work-carrying container comprised of interlocked horizontally disposed sections, 1 a removable cover on said retort, a driving motor supported on said cover, a shaft extending from said driving motor and projecting through said cover, and a fan car- 'ried by said shaft interiorly of said retort for creating a forced circulation of gas within said retort.

4. A retort furnace comprising in combination a furnace chamber, a heating means surrounding said chamber, a retort insertable into or removable from said furnace chamber, a perforated charge carrying container comprised of interlocked horizontally disposed sections, a driving motor supported on saidcover, a shaft extending from said driving motor and projecting through said cover, and a fan carried by said shaft and disposed within said retort for establishing a forced circulation of gas within said retort.

5. A retort furnace of the character described comprising an enclosure having an' opening therein and constituting a heating chamber, a retort removably supported in said heating chamber and spaced from walls thereof and having means cooperating with the opening of said enclosure for closing and sealing said heating chamber, a removable cover attached to and movable with said retort for closing and sealing said retort, and means carried b and removablawith said cover for force ully circulating fluids; within said retort.

6. retort furnace of the character described comprising an enclosure having side walls, a bottom, and a heating chamber with an open top, a retort removably supported in said heating chamber and spaced from said side walls and having means cooperatin with the upper portlons of said side wa ls for closing and sealing said heating chamber, a removable cover attached to and movable with said retort for closing and sealing said retort and means carried by and removable with said cover for forcefully circulatin fluids within said-retort.

7. A retort urnace of the character described comprising an enclosure having an opening therein and constituting a heating chamber, a retort removably supported in said heating chamber and spaced from walls thereof and having means .cooperating with the opening of said enclosure for closing and sealing said heating. chamber, a removable cover attached to and movable with said retort for closing and sealing said retort, and means carried by and removable with said cover for containing and introducing into said retort, a substance productive of a processing atmosphere.

8. A retort furnace of the character described comprising an enclosure having side walls, a bottom, and a heating chamber with an open top, a retort removably supported in said heating chamber and spaced from said side walls and having means cooperating with the upper portions of said side walls for closing and sealing said heating chamber, a removable cover attached to and movable withsaid retort for closing and sealing said retort and means carried by and removable with said cover for containing and introducing into said retort, a substance productive of a processing atmosphere.

9. A retort furnace of the character described comprising an enclosure having an opening therein and constituting a heating chamber, a retort removably supported in said heating chamber and spaced from walls thereof and having means cooperating with the opening of said enclosure for closing and sealing said heating chamber, a removable cover, attached to and movable with said retort for closing and sealing said retort, and means carried by and removable with said cover for containing and. introducing into said retort, a substance productive of' a processing atmosphere and for forcefully circulating fluids within said retort.

10. A retortfurnace of the character described comprising an enclosure having side walls, a bottom, and a heating chamber with an open top, a retort removably supported in said heating chamber and spaced from said side walls and having means cooperating with the upper portions of said side Wallsfor. closing and sealing said heating chamber, a removable cover attached to and movable with said retort for closing and sealing said retort, and means carried by and removable withsaid cover forcontaining and introducin into said retort, a substance productive o a processing atmosphere and for forcefully circulating fluids within said retort.

- 11. A retort furnace comprising a heat insulated enclosure, a sealed retort removably supported'in said enclosure provided with means forming a seal for said enclosure and having a removable cover attached to and removable with said retort for closing and sealing said retort, and means within said retort carried by said cover for forcefully circulating fluids therein.

12. In a furnace, the combination of a furnace chamber, a vertical retort insert able into and removable from said furnace chamber, a cover member bodily movable with said retort and adapted to close and seal one end of said retort both when said retort is in and when said retort is removed from said furnace, a drive shaft projecting through said cover member, a drive motor carried by said cover connected with said drive shaft exteriorly of said retort and means connected with said shaft interiorly of said retort for forcibly agitating fluids in said retort.

13. A retort furnace of the character described, comprising a heating chamber and a removable, sealed retort, adapted to be supported in said chamber a work holder in said retort spaced from the walls thereof, providing in said space, an elongated annular heating passage, means in the top of said retort for operation when the retort is sealed for forcing the down passage of fluids through said annular space and means for introducing fluids adjacent the top of said retort and into the forced downward travel of fluid effected by said first means,

said work holder being constructed and positioned in the path of a reverse, return flow of the fluid in circulation whereby fluids in said retort are given an initial travel in one direction through a heating space and are caused by forced circulation, to undergo a.

rapid reversal in direction of flow and come in immediate contact with the work to be treated, held in said work holder.

14. In a retort furnace, a heating chamber, a removable closed retort adapted to be positioned in heat transferring association in said heatin chamber and while closed to be remove out of said chamber, a work container in said retort, having walls spaced apart fromvthe walls of said retort to provide a. heating space, and means in said retort for providing a forced circulation of fluids in said retort first downwardly through said heating space and thence up.- wardly through said work holder and means at the top of said work holder for restricting the circulation of fluids out of said work holder whereby a crowding of the circulated fluid may be effected in said work holder.

In testimony whereof I aflix my signature.

FRED A. HANSEN. 

